Dŵr Cymru Welsh Water is putting out a strong message to young people about the potentially fatal consequences of swimming in reservoirs.

Welsh Water’s One Last Breath video campaign starkly depicts two teenagers who drown after going into the water at a reservoir on a hot summer day – and the impact on their friends and family left behind.

Every year, large numbers of people – predominantly young men aged between 17 and 35 – attempt to swim in our reservoirs across Wales.

Last summer alone, there were 109 incidents where people tried to enter the water – while two people died when swimming at reservoirs in the Brecon Beacons across the same weekend during a heatwave in 2013.

Welsh Water, which serves most of Wales and Herefordshire, is issuing the warning about the extreme danger of swimming in reservoirs because of freezing temperatures, deadly under-currents and hidden machinery that can drag the strongest swimmers under.

The campaign has been developed after working with Maxine, Reuben’s mother who tragically died after going missing when swimming at Pontsticill Reservoir, near Merthyr Tydfil.

The Cyfarthfa High School pupil had been camping at the reservoir with friends when he went swimming and got into difficulties.

Welsh Water’s Chief Operating Officer, Peter Perry, said: “Our reservoirs are great places to enjoy organised activities but all too often people are tempted to risk taking a swim which can lead to tragic consequences.

“While reservoirs might seem like a great place to cool off, they are full of hidden dangers with freezing cold water and strong currents.

“We ask customers to remember that reservoirs are working sites that are an important part of the water cycle. This is why we display signage at these sites and undertake campaigns asking customers not to swim at any time.”

Reuben’s mother, Maxine Johnson, said: “They couldn’t pinpoint where he was in the reservoir, which was really traumatic.

“I was a bit naïve. I didn’t think he’d go in the water, why I didn’t think that I don’t know, because he was a very adventurous boy.

“He thought he was invincible – he was a very strong, fit boy and he had the stature of a man and worked out in the gym.

“I suppose he thought he’d be able to get across. For Reuben it was the coldness of the water, the freezing temperatures, which killed him.”